Endeavour Drive - Drivability analysis |
Endeavour Drive - Drivability analysis |
Sep 18 2008, 11:05 AM
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#201
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
http://www.sciencefriday.com/program/archives/200809191
You can listen via NPR, or via one of the web feeds that are listed on the site, but make sure you do listen if you can. |
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Sep 24 2008, 06:02 PM
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#202
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Member Group: Members Posts: 293 Joined: 22-September 08 From: Spain Member No.: 4350 |
I played with the same image than fredk using GIMP and got this:
I pixelated copies of the image to a few square sizes between 10 and 25px, stretched them from black to white and stacked them at 50% transparency (bigger dunes seem to make brighter averages, but if a square boundary catches half a dune, you get an artifact), then gaussian blurred it at 25px, adjusted brightness and contrast, applied a color degradation map and overlayed it on the original image. |
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Sep 24 2008, 08:02 PM
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#203
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Senior Member Group: Members Posts: 4252 Joined: 17-January 05 Member No.: 152 |
I played with the same image than fredk using GIMP and got this: Nice job. I had noticed that areas with bigger dunes tend to be brighter, so a simple blurring might work. But you might need to worry about trends in suface brightness, ie some areas with ripples of size x may be brighter on average than other areas with ripples the same size. To deal with this some Fourier type method or a simple variance as I did may be more robust. |
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Sep 24 2008, 08:27 PM
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#204
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Member Group: Members Posts: 293 Joined: 22-September 08 From: Spain Member No.: 4350 |
Grain sorting may be a factor. The albedo of the dunes won't be constant if they are topped by dust. Maybe that's why bigger dunes are brighter on average.
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